[Asterisk-Users] a few questions about sip implementation

[Simon J Mudd]

jtodd at loligo.com (John Todd) writes:

>    There are certainly some things that are lacking with Asterisk's
> SIP implementation, some of which you may have tripped over.  Of
> course, Asterisk's SIP stack is "pragmatic" and has been developed as
> people discover needs for particular functions.

Ok.  Perhaps I can help with making fixes where they are
appropriate. Also I'm looking at the latest SIP RFC, previous RFCs may
have said different things.

> However, there are
> perhaps some solutions to your questions:
> 
> >I'm looking at RFC 3261, I think the latest SIP standard and have a few
> >questions about the * sip implementation:
> >
> >1. 8.2.6.1 Sending a Provisional Response says that UASs SHOULD NOT issue
> >a provisional response to non-INVITE requests.
> >
> >>From my message yesterday * appears to be sending a SIP/2.0 100 Trying to
> >X-Lite's REGISTER request before sending the SIP/2.0 200 OK message.
> >
> >Is this correct?
> 
> Yes, that is what it is doing and and while it may not adherent to the
> exact reading of the RFC, I have seen several other proxies doing the
> same thing (examples: FWD's SIP proxy (Cisco?) does send "100 Trying"
> but SER does not) so I will assume it's an awkward industry standard,
> though perhaps not exactly compliant to the RFC paragraph that you
> describe.

Ok.  Apparently the trying should be sent for everything except
REGISTER. Not too sure why.

> >2. 10.3 Processing REGISTER requests. The 5th paragraph states "that the
> >registrar has to know the set of domain(s) for which it maintains
> >bindings".
> >
> >How is this specified in Asterisk?  Through the context?  ie should the
> >domains be specified in sip.conf via the context parameter, of the
> >form context=domain.com?
> 
> Currently, that is not possible.  The registrar maintains the set of
> allowed bindings by an exactly matching username/password process, OR
> via an IP-based permissions scheme.  There are no wildcards for
> domains in Asterisk for authentication.  This does not preclude you
> from creating entries for each SIP user in your sip.conf file, which
> is a bit tedious, but may be an interim solution.

Ok.  I guess a realm=zxxxx entry might be sufficient as the SIP client
when authenticating will have an address of the form To:
sip:1234 at realm.com rather than @IP of the client. (I think).  if the
information could be stored then it could be used.

> >3. I have another SIP account (sip:912345678 at domain.es) which I would like
> >to use within asterisk both for dialing out and for receiving calls.
> >
> >I see that sip.conf has a line
> >
> >register => 912345678 at domain.es/1234
> >
> >where 1234 is the local asterisk extension.  From chan_sip.c, line 1390 I
> >see that I can use the form:
> >
> >register => user[:secret[:authuser]]@host[:port][/localextension]
> >
> >However my registrar requires that I authenticate with domain.es, but use
> >a sip proxy at ip 1.2.3.4, the two are unrelated and domain.es has no ip
> >address.  How can I get Asterisk to register with the remote prxoy?
> 
> I sent a note to Mark about this.  We had discussed a patch to fix
> this back in Feb, but apparently it didn't do quite the trick (due to
> my lack of testing.)  Lines like this are supported:
> 
> register => 9993 at something.foo.net:password at blatz.filbert.com/9993
> 
> However, the current REGISTER routines don't chop off
> "blatz.filbert.com" in the To: and From: fields.  Hopefully a repair
> will be seen in the future.

Ok. I hadn't understood the source too well in that respect as there
was also the :port bit mentioned.  if this format

register => 993 at realm.com:password at proxy.realm.com:port/localpart is
acceptable I can look at modifying the existing source to accept this
format and using it appropriately.  That shouldn't be too hard (I
think).

Thanks for the feedback.

Simon